National Ambient Air Quality Standards for Ozone

To protect human health and welfare from damaging levels of air pollution, the Clean Air Act of 1970 established a process for setting National Ambient Air Quality Standards (NAAQS) for ozone, as well as several other air pollutants. In the case of ozone, a standard for a one-hour average concentration of 120 parts per billion was set for protection from intense short-term exposures. In 1997, under President Clinton, the U.S. Environmental Protection Agency promulgated a more protective eight-hour average ozone standard of 80 parts per billion on the basis that longer-term exposure to elevated levels of ozone can be just as damaging, if not more damaging, than shorter exposures to very high levels of ozone. DES supports the more stringent standard but the implementation of the eight-hour standard has been delayed by litigation from major utility and industry groups. Read more about this issue and the effects of the litigation on New Hampshire's air quality.

The Clean Air Act Amendments of 1990 require DES to submit a technical analysis to show how the state can achieve compliance with the one-hour NAAQS for ozone. This analysis was submitted as the One-Hour Ozone Attainment Demonstration in 1998 and includes descriptions of reduction programs that New Hampshire is or will be undertaking to achieve attainment with the ozone standard. Demonstrating compliance with the ozone standard is not strictly a matter of reducing emissions within the state since much of the ozone (and its precursors) that we experience here in New Hampshire is transported in from other regions upwind of the state. New Hampshire has already done much to reduce our emissions of ozone-producing compounds but other states have done little to clean up the dirty air, which eventually makes its way to the Northeast. To insure that other regions do their fair share in reducing pollution, DES in 1997 filed a petition under Section 126 of the Clean Air Act to show that attaining the ozone standard in this state depends on reductions in ozone precursor emissions in other states. New Hampshire's Petition for Abatement of Excessive Emissions is available on this website and contains a detailed analysis of the effects of emissions from other regions on New Hampshire's air quality.